Hot-water mask-washing machine

ABSTRACT

Masks to be cleaned are immersed in a tank in which liquid circulation is maintained at and past the masks, and over a filtering weir. This circulation is induced by a high-volume, low-pressure, and low-velocity system that creates a gravity pressure head to maintain the circulation with a minimum of energy loss. In the preferred form of the machine, the pressure system centers in a shrouded axial-flow propellor driving downward the liquid in a low-pressure portion of the tank to establish the pressure head differential. Provision is made for controlling the deposit of condensate accumulating on the cover of the heated tank.

United States Patent 1 1 [111 Szcze anski Oct. 28 1975 [54] HOT-WATERMASK-WASHING MACHINE 3107,167 9/1965 Edslrom 134/200 X [76] Inventor:Harry Szczepanski, 900 Clancy NE.,

Grand Ra id Mi h 49505 Primary Examiner-Robert L. Bleutge Filed p 4 1974Allorney, Agent, or Firm-Glenn B. Morse, Esq.

21 A l. N 1 pp 457 57 ABSTRACT R l d A 62 gate U S pphcamm Masks to becleaned are immersed in a tank in which 1 gs' g' g g liquid circulationis maintained at and past the masks, and over a filtering weir. Thiscirculation is induced by a high-volume, low-pressure, and low-velocitysystem ii ig g gl that creates a gravity pressure head to maintain the[58] Field I62 200 circulation with a minimum of energy loss. In thepre- 1321/20 ferred form of the machine, the pressure system centers ina shrouded axial-flow propellor driving downward the liquid in alow-pressure portion of the tank [56] References cued to establish thepressure head differential. Provision is UNlTED STATES PATENTS made forcontrolling the deposit of condensate accu- 1,312 414 8/1919 Monte134/162 X mulating on the cover of the heated tank. 1,896,648 2/1933Thomasmu 134/143 X 2,995,851 8/1961 Dirats 134/135 X 1 Claim, 16 DrawingFigures 6O 59 O I 58 1 o I 55 35 I 36 i1 1 3e 19' as 1 I 1' l I 57 22 il as t 1 I I 23 a v 72 67 1 24 1 2a U.S. Patent Oct. 28, 1975 Sheet 1 of12 US. Patent Oct.28,1975 Sheet4of 12 3,915,181

U.S. Patent Oct.28,1975 Sheet5of12 3,915,181

US. Patent Oct.28,1975 Sheet6ofl2 3,915,181

Patent 00. 28, 1975 Sheet 7 of 12 US. Patent 0:.2s, 1975 Sheet8of 123,915,181

mm Wm U.S. Patent Oct.28,1975 Sheet9of 12 3,915,181

Fig. IO

US. Patent Oct. 28, 1975 Sheet 10 of 12 3,915,181

US. Patent Oct.28,1975 Sheet 12 of 12 3,915,181

0 0.0000000 :00 cocoa 0 00000000 HOT-WATER MASK-WASHING MACHINEBACKGROUND OF THE INVENTION This is a division of Application Ser. No.243,601, filed Apr. 13, 1972 now Pat. No. 3,812,869.

Masks used in spray-painting procedures must be cleaned periodically toremove deposits of paint over the areas where the mask has interruptedthe flow of paint onto the work pieces. Two different procedures havebeen developed for this cleaning operation. One of these is to immersethe masks in a conventional solvent for whatever types of paint havebeen involved. The second procedure is more recent, and centers in thecoating of the masks initially with a material which is solidified atroom temperature, but becomes liquefied at temperatures below theboiling point of water. A mask coated with this material, and then usedin spray-painting operations, accumulates the paint on the outside ofthe coating material, so that the paint can be removed by liquefactionof the coating material and the consequent release of all materialaccumulated on top of the coating. The liquefaction of the coating isnormally provided by immersion of the mask in hot water. Both thesolvent and hot-water cleaning procedures will normally involve pumpingsystems of some sort for maintaining a circulation across the masks tofacilitate the removal of the accumulated materials. Where theliquefiable coating is used, the mask is re-coated during or after thecleaning operation has been completed.

The arrangements for maintaining the circulation of the solvent or hotwater within the cleaning tank have usually involved pumps and pipingoperating at relatively high pressures, which produces a variety ofproblems. One of these is the cost of the pumps and the piping(including installation), and the other is the maintenance of adequatecirculation in the presence of the relatively high losses necessarilyassociated with piping conducting liquid at substantial velocities.Maskcleaning operations usually require a circulation which moves a highvolume of liquid, and the confinement of this volume within piping ofreasonable size results in the velocities tending to produce high energylosses. These losses are responsible for the necessity of using pumps ofconsiderably greater power and pressure capacity than would seem to benecessary in the working area of the machine.

It is the usual practice to provide tank-type cleaning machines with arelatively stagnant area somewhere in the liquid circulating systemwhere entrained particles have an opportunity to settle out. Thesesettling basins are periodically cleaned out with shovels or scrapers,producing the usual cost and machine down-time associated with manualservicing operations. It may be noted in passing here that theseparation of entrained paint particles from the cleaning liquid hasbeen facilitated by the recent developement of additives which kill thepaint, in the sense that the paint is altered from a sticky consistencyto a rubbery material which does not tend to adhere to surfaces on whichthe entrained particles may impinge. In conventional maskcleaningmachines, this new development has both advantages and disadvantages.While the removal of entrained particles is more complete, theaccumulation of these in the settling basins is also more rapid.

SUMMARY OF THE INVENTION The present invention has been directed at theproblems noted above. Masks are immersed in a tank in which alow-pressure and high-volume circulation is maintained at and past theimmersed masks. Substantially the entire circulation path of the liquidis traversed with a low, but sufficient velocity to eliminate anytendency for the entrained particles of paint to settle out. In contrastto the settling-basin arrangement for removing the particles, thepresent invention utilizes a filtration weir traversed preferably by theentire circulation in the tank. The weir structure involves an overflowpoint in a partition separating the tank into high and low-pressuresections, and a perforate panel extends at a downward inclination fromthe partition permitting liquid to fall through into the low-pressuretank portion. Particles of a size in excess of that permitted to passthrough the perforate panel are moved downwardly by the overflow, andultimately fall into a filtration bag which can be removed periodicallyand emptied. The particular angle of downward inclination of theperforate panel is preferably selected so that almost all of the liquidwill fall through the panel, leaving just enough flow to continuallyurge the particles entrapped on the panel to roll downwardly into thebag.

The system for maintaining the circulation of the liquid in the tankcenters in a shrouded axial-flow propellor, which is preferably orientedto drive liquid taken from the low-pressure side of the tank in adownward direction. The liquid is then diverted across the bottom of thetank and upward into a manifold extending along a vertical wall of thetank. A number of openings are provided in this manifold, which producesa pattern of discharge parts directing the tank liguid laterally againstthe masks. The masks are disposed at an angle which produces adeflection of the liquid in an upward direction generally toward theoverflow weir, which facilitates the maintenance of removed particles insuspension, and inhibits the collection of these on the bottom of thetank. A placement of the masks in a spaced relationship to the bottom ofthe tank also provides a degree of flow velocity directly along thebottom which further tends to minimize the possibility of accumulationof particles in this area, particularly when in conjunction with acurved and inclined configuration of the tank surfaces in this areatending to maintain this relatively low velocity, compared to that ofhighpressure jets in conventional machines. Where the machines are usedin conjunction with the hot-water cleaning procedures, the cover on thetank is actuated to the open position by a mechanism which tilts thecover into a position where accumulations of condensate fall inward intothe tank area in a position where they do not impings on cleaned maskswhich are being dried after being removed from the tank.

DESCRIPTION OF THE DRAWINGS FIG. I is a front perspective view of themachine, showing the operating condition of the machine with the tankcover closed.

FIG. 2 is a front perspective view from the opposite side of the machinefrom that of FIG. I.

FIG. 3 is a rear perspective of the machine, from the same side as thatof FIG. 1. Access covers have been removed from the rear of the machineto expose the interior arrangement.

FIG. 4 is a front elevation of the machine shown in FIGS. 1 to 3.

FIG. 5 is an end elevation of a modified form of the machine from thatshown in FIG. 4.

FIG. 6 is a partial sectional front elevation of the machine illustratedin FIG. 4, on an enlarged scale.

FIG. 7 is a fragmentary sectional elevation at the rear of the machineshown in FIG. 4.

FIG. 8 is a top view of the machine shown in FIG. 4, on an enlargedscale.

FIG. 9 is a sectional view taken of the plane 9-9 of FIG. 11, which is ahorizontal plane.

FIG. 10 is a vertical sectional view through the machine, taken at theplane 10-10 of FIGS. 4 and 9.

FIG. 11 is a sectional elevation on the plane 11-11 of FIGS. 4 and 9.

FIG. 12 is a vertical sectional view taken at the plane 12-12 of FIGS. 4and 9, with the cover and the mask rack in the elevated position.

FIG. 13 is a perspective view of the perforate panel extending from theoverflow weir.

FIG. 14 is a perspective view of a filter bag placed at the down streamend of the perforate panel shown in FIG. 13.

FIG. 15 is a fragmentary sectional elevation on the plane 15-15 of FIG.16, showing the structural details of the filtration system.

FIG. 16 is a fragmentary rear view of the filter bag and perforate weirplate taken at the plane l6--l6 of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The machine illustrated in FIG.1 and the related figures has an upper housing 20 and a tank structuregenerally indicated at 21. Referring to FIG. 10, the tank structureincludes the exterior paneling 22, the watertight interior liner 23, andthe insulation 24 interposed between these components. Conventionalelectric heating probes 25 and 26 traverse the rear portion of the tank,and extend adjacent the bottom of the liner 23 to maintain an elevatedtemperature of the liquid in the tank. The machine illustrated in thesedrawings is adapted primarily for the use of hot water. and inconjunction with masks coated with a releasable material that isliquefied by temperatures on the order of 180 to 200F.

The opposite guideways 27 and 28 (refer to FIGS. 1 and 2) are mounted onthe housing 20, and extend downward into the tank area as illustrated inFIG. 12. Carriage units 29 and 30 engage these guideways, and areinterconnected by the beam 31. Brackets as shown at 32 in FIG. 12 aresecured to the carriages 29 and 30 to support the rack structure 33 onwhich masks are placed for immersion into the tank. This rack structureis formed by the lower rail 34 and the upper rail 35 interconnected bythe end members 36 and 37 and the series of spaced rods 38 arranged invertical planes.

The vertical movement of the mask rack becomes evident by comparison ofFIGS. 10 and 12. The mechanism responsible for this movement is mountedon the top of the housing 20, and is illustrated in FIG. 8. The cylinder39 is secured to the top 40 of the housing, and the piston rod 41carries the pulley 42 rotatably mounted in the fork 43 secured to theend of the piston rod 41. Cables 44 and 45 extend from the bracket 46secured to the top 40 of the housing around the double pulley 42. Thecable 45 extends to the pulley 47 rotatably mounted in the bracket 48,and the pulley 44 around the idler pulley 49 rotatably supported by thebracket 50 and to the pulley 51 rotatably mounted in the bracket 52.These brackets are all secured to the top of the housing 40, and thepulleys 47 and 51 change the course of the cables 45 and 44,respectively. downwardly to points of connection with the carriages 29and 30 within the guideways 27 and 28. Extension of the piston rod 41will therefore result in lowering the mask rack, and retraction of thepiston rod 41 will raise the mask rack to the position shown in FIG. 12,both at a two-to-one movement ratio of the rack with re spect to thepiston.

The cover 53 is preferably constructed of spaced stainless steel sheets54 and 55 separated by the insulation 56. This cover rests on the shelfstructure 57 defining a top opening in the tank. The closed position ofthe cover is illustrated in FIG. 10. The raising of the mask rack movesthe cover to the open position shown in FIG. 12 by the action of thebrackets 58 secured to the carriages 29 and 30, respectively. Thesebrackets have supporting flanges 59 which engage the underside of thecover 53, and are disposed at an angle (to the closed position of thecover) downwardly to the rear, as shown in FIG. 12, so that condensateaccumulating on the underside of the cover will move downwardly alongthe cover and drip off into the tank at the rear portion of the openingdefined by the shelf 57. The bolts 60 are fixed with respect to thecover 53, and loosely engage a suitable hole in the flange 59 to preventlateral displacement of the cover with respect to the brackets 58. Thelateral extension of the cover 53 is beyond the vertically-projectedboundaries of the mask rack structure, so that the movement of dropletsof condensate downwardly along the cover to the rear edge provides ashelter for the masks carried by the rack structure. Masks are thereforepermitted to dry in the position of the machine shown in FIG. 12, andthey may be re-sprayed with coating material in this position. Thisstage of the process can take place without contamination by droplets ofcondensate.

A circulation of water within the tank structure is maintained by thepump system shown best in FIGS. 7 and 11. An axial-flow propellor 61 ismounted on the shaft 62, the lower end of which is supported in thebearing 63. This bearing is located with respect to the propellor shroud64 by radially-extending and angularly-spaced legs 65. The shroud 64 issupported on the central structure 66 secured to the floor of the tank,this structure having an opening registering with the inside of theshroud 64 to provide a passage for the flow of liquid under the actionof the propellor 61. Flow is conducted downward to the propellor 61through the conduit 67, and extends from the discharge point of theshroud 64 into the bottom ducts 68-70 which are integral with thestructure 66. (Refer to FIG. 9.) These feed ducts provide a supply ofliquid to the vertical discharge duct defined by the wall of the tankand the perforate panel 7]. (Refer to FIG. 11.) The openings in thispanel function as exhaust ports directing a plurality of streams ofliquid laterally from the front to the rear of the tank at and past therack structure and any masks which happen to be supported by it. Theangular orientation of the front surfaces of the rails 34 and 35 of themask rack have a tendency to deflect flow upwardly as it moves to therear toward the top of the inclined partition 72 in the tank, whichseparates the tank into high and low pressure areas. The top of thispartition forms an overflow point from the front high pressure portionof the tank to the rear low-pressure portionhaving a lower staticpressure head (shown at 73 in FlGI it); than that shown at 74 associatedwith the front portion of the tank. The duct 67 intersects the tankpartition 72. and forces the liquid overflowing from the opposite sidesof the partition to follow the flow path shown in FIG. 7. The lowerextremity of the duct 67 is open; and its presence tends to equalize theinflow of liquid into the top of the propellor' shroud 64. it ispreferable to incorporate arcuate corners as shown at -77 in FIGS. 7 and11 at the turns in the liquid flow to reduce losses as much as possible.l

The removal of entrained particles of paint is accomplished by thestructure shown in FIGS. 10 and l316. This structure is duplicated atthe opposite sides of the machine. and includes the perforate weirpanels 75, which extend downwardly from the edge of the partition 72along a distance defined by the spacing of the integral end-plates 76and 77. The lower edge 78 of these perforate panels is placed over theedge of the filtration bags 79 having the handle rods 80 and 81 securedto the marginal edges of the bags, and extending to provide support forthe bag by interengagement of the horizontal portions of the rods withthe shelves 82 and 83 shown in FIG. 7. The bags 79 are within the low'pressure portion of the tank, and the inclination of the perforate plate75 is selected preferably so that water overflowing at the upper edge ofthe plate continues in diminished quantity to a degree such that just asum cicnt amount of liquid flows over the lower edge 78 to carry with itparticles of paint that have been entrapped on the plate, and carry theminto the collecting bag 79. This bag functions as a filter, and permitsaccumulations of liquid to return to the low pressure portion of thetank along with that passing through the perforate panel 75. This panelacts as the floor of an overflow conduit.

Ventilation for the machine is provided by the blower system shown bestin FIG. 11. The shaft 62 carrying the propellor 64 extends upwardlythrough the bearing 84 mounted on the tank structure, and also throughthe bearings 85 and 86 carried by the stanshaped brackets 87 and 88secured to the exhaust ducting 89 mounted on the top of the housing 20.The shaft 62 may be provided in a plurality of sections interconnectedby couplings as shown at 90, if desired. A pulley 91 is fixed withrespect to the shaft 62, and carries one or more belts 92 to the pulley93 on the motor 94 through a suitable opening 95 in the exhaust ducting89. The blower impellor 96 is preferably an axial flow unit, and isdriven along with the propellor 61 by the motor 94. Op-- eration of theblower system establishes a reduction in pressure in the exhaust ducting89 producing a suction tending to purge the tank area, and also thespace at the rear of the partition 72. An opening 97 is provided in theinclined central panel 98 causing the reduction in pressure to removeaccumulations of vapor in this area. The lower perforate panel 101 atthe rear communicates with the interior of the vertical exhaust duct 100via the passage defined by the panel 101 and the access covers 102(refer to FIG. 11). These arrangements also provide for the continualremoval of vapors when the covers 102 (refer to FIG. 10) are removed.and prevent seepage of the vapors around these covers so that lockedfits and seals are not necessary.

y The exterior.arrangement of the machine is altered slightly in themodification shown in FIG. 5, which is functionally similar to that.previously described. but has. a separate drive for the fluidcircu|ationsystem from thatol the blower. in thc FIG. 5 arrangement. a separatepump unit 103 is secured to the top of the tank 104, in place of thearrangement in which the pump may be driven by the same shaft as that ofthe blower. The blower; within the housing 105 is driven by the motor106 in the same fashion as that shown in FIG. 1 I. The upper housing I07and its contents are similar to those previously described: Theequipment installed on the end of the machine illustrated in FIG. 2includes the usual motor controis. starters. switches. junction boxes.and other items indicated at random at l08l l l. and the opposite end ofthe machine shown in FIG. 1 provides a convenient place for theinstallation of control components associated with the pneumatic and hydraulic actuating system. These items are conventional. and areindicated generally at 112-415. It is also pret erable to incorporaterelatively heavy parallel rectangular tubes 1 16 and 1 [7 into thebottom of the machine to receive the tines ofa fork lift to facilitatemoving the machine from place to place.

Applicant has found that it is preferable to operate a machine of thistype in a so-called two-stage" procedure. in which masks are cleanedannd dried by the ma chine (with the drying operation taking place whilethe mask rack is in the FIG. 12 position, and with the assist ance ofdraft induced by the blower). followed by an application of a newcoating with hand-held spray gun equipment while the masks are in thisposition. in single-stage operations, attempts are made to incorporatere-coating materials in the cleaning solution within the tank. but theaccommodation ofthe machine to various types of paint with this systemhas provcn to be some what difficult over extended periods of operationThere is considerable difficulty in maintaining the chemical stabilityof the tank solution, which ceases to be a problem when the twostageprocedure is used. Depending upon the particular paint material beingremoved from the masks, and the degree of accumulation on the masks,cleaning time /iiVllFiCd with Aimachinc of the type illustrated in thesedrawings from between 30 seconds to as high as 7 minutes. The latterapplies to the more difficult materials to remove such as the vinyls.With the 2 -stage system. the tank can contain es sentially tap water,with a small percentage of additive to make up the initial bath for thepurpose of converting the paint particles to a non-sticky consistency.With the usual paint materials modified by this additive, the perforatedweir panels can be provided with holes of approximately a quarter of aninch in diameter. with the panel disposed at a downward inclination ofbe tween 15 and 30. The depth of the overflow stream at the high pointof the perforated weir panels was approximately %ths to /4th5 of aninch. Many particles will actually fall through the weir openings ofthis diameter, but continued operation of the machine will result in thetendency to progressively eliminate these as the water is continuallyrecirculated along paths that con tain no points of stagnation. it ispreferable to allow about th to 174 th of an inch in depth of water tooverflow into the collecting bags to continually produce the desirabletendency to tumble particles en trapped on the inclined weir panelsdownward into the bag. The pressure head differential induced by theoperation of the propellor 61 is preferably selected at approximately 6inches. and the level in the tank can be determined by a conventionalfloat valve (not shown) operative to control a supply pipe communicatingwith any convenient place on the tank. in view of the relatively smallloss of liquid through vapor, the filling of the tank can also becontrolled manually. if desired.

I claim:

1. An immersion-processing machine including a tank, having an openingand a cover for said opening, and a rack for supporting articles forimmersion in said tank, and also including an elevating mechanismoperative to raise said rack, wherein the improvement comprises:

8 opening means carried by said elevating mechanism and engageable withsaid cover to raise said cover substantially continually within thespace defined by the vertically projected area of the closed position ofsaid cover on upward movement of said rack, said opening meanssupporting said cover in an inclined position with respect to the closedposition of said cover as supported by said tank, said cover extendinglaterally beyond the vertically projected boundaries of said rack, andthe lower edge of said cover in the inclined position thereof beingwithin the vertical projection of the opening in said tank associatedwith said cover.

1. An immersion-processing machine including a tank, having an openingand a cover for said opening, and a rack for supporting articles forimmersion in said tank, and also including an elevating mechanismoperative to raise said rack, wherein the improvement comprises: openingmeans carried by said elevating mechanism and engagable with said coverto raise said cover substantially continually within the space definedby the vertically projected area of the closed position of said cover onupward movement of said rack, said opening means supporting said coverin an inclined position with respect to the closed position of saidcover as supported by said tank, said cover extending laterally beyondthe vertically projected boundaries of said rack, and the lower edge ofsaid cover in the inclined position thereof being within the verticalprojection of the opening in said tank associated with said cover.